1. Field of the Invention
This invention relates to an anamorphic attachment to be used in conjunction with a basic lens.
2. Background Information
A picture has an aspect ratio, which is the ratio between the image width and height. Motion pictures were originally recorded on film where the image area had an aspect ratio of 4:3 (1.33:1), sometimes referred to as academy ratio. To accommodate the addition of a soundtrack, the standard ratio for filming was adjusted slightly to be 1.37:1. Television also uses a 4:3 aspect ratio.
To enhance the theatrical cinematic experience, various methods have been devised to present a motion picture that is wider than a 4:3 ratio. Some common presentation formats and the percentage increase in width over academy ratio are as follows:
CinemaScope .RTM. 2.55:1 192% Panavision .RTM. 2.40:1 180% Super 35 2.34:1 177% Flat widescreen U.S. 1.85:1 139% High-definition television 1.78.1 134% Flat widescreen Europe 1.66:1 125%
Presentation of motion pictures with a wide aspect ratio is sometimes accomplished by masking the full frame of the image on the media to be displayed to produce the desired image ratio. This process is often called flat widescreen. While this requires minimum modification to the projector to display a wider image than academy ratio, the object being projected is smaller. This results in a projected image that is not as bright and is of lower quality than an image of the same height projected from the full frame of the display media.
Flat widescreen presentations from film media using modern projectors achieve acceptable quality levels. However, emerging projection technologies for digitally encoded motion pictures use display media that presently cannot provide the resolution of film. The loss of resolution inherent in a flat widescreen process makes masking of the projected object undesirable with such projection technologies.
Another method of presenting a wide motion picture is the anamorphic process. The image to be projected is compressed horizontally to fit in a full frame by using anamorphic optics, or by other means such as electronic image manipulation. The image is then expanded by corresponding anamorphic optics on the projector which provide greater magnification horizontally than vertically to produce the appropriate display aspect ratio. It should be noted that, while it is convenient to speak in terms of compressing when recording and expanding when reproducing along one axis, the same result can be achieved by compressing when recording along one axis and compressing when reproducing along the perpendicular axis. It is also possible to use expansion in both processes rather than compression. Thus, the recording lens may either have a reciprocal anamorphic ratio to the reproducing lens with the anamorphic effect of both applied along the same axis, or both lenses can have the same anamorphic ratio applied along perpendicular axes.
Anamorphic systems produce presentations of a high quality, but the necessity for the additional anamorphic optics increases the cost of the projector. Anamorphic lens attachments generally provide only a single ratio of anamorphic effect. Therefore, a different anamorphic attachment is required to provide the appropriate anamorphic ratio for every format that is to be presented with an anamorphic process.
The use of anamorphic optics to provide a variety of display aspect ratios is particularly beneficial for systems based on emerging digital display technologies because all available resolution of the recording and display media can be utilized. Further, some digital media use ratios other than academy ratio. For example, media with a 1280 by 1024 element resolution has a ratio of 1.25. Without anamorphic optics, a 4:3 ratio image could use only 963 elements vertically, while a 1.85:1 flat widescreen image would use only 692 vertical elements. By using anamorphic optics with an anamorphic ratio of about 1.07:1, a 4:3 ratio image can utilize the full 1024 element vertical resolution.
It would be desirable to use an anamorphic process to display a variety of formats that are wider than academy ratio to enjoy the benefits of brighter images of higher quality without the expense of a large number of anamorphic lens attachments. This is especially desirable for emerging digital projection technologies where all available resolution is needed. Accordingly, there is a need for an anamorphic attachment with a variable anamorphic ratio for use in recording or projecting images with aspect ratios that differ from the aspect ratio of the image area on the recording or display medium.